In a speech delivered at the Truman Presidential Museum and Library in Independence, Mo., billed as his last address to an American audience as secretary-general, Annan said, "You Americans did so much, in the last century, to build an effective multilateral system, with the United Nations at its heart. Do you need it less today, and does it need you less than 60 years ago?"

Annan did not directly cite the Bush administration, with which he has had a fraught relationship, but he made his rebuke of current U.S. foreign policy clear by urging a return to "farsighted American leadership, in the Truman tradition."

Annan noted that the United States was "in the vanguard of the global human rights movement," but said "that lead can only be maintained if America remains true to its principles, including in the struggle against terrorism."

"When it appears to abandon its own ideals and objectives," he added, "its friends abroad are naturally troubled and confused."

Annan steps down Dec. 31 after completing his second five-year term to be succeeded by Ban Ki-moon.

Annan has often been at odds with the Bush administration, particularly since the United States invaded Iraq in 2003 without obtaining a go-ahead from the United Nations.

Having infuriated the Bush administration two years ago by labeling the Iraq war "illegal," he said Monday that while observing international law can be "inconvenient," it is essential.

In a clear reference to the lack of international support for the U.S. action in Iraq, Annan said, "No state can make its own actions legitimate in the eyes of others. When power, especially military force, is used, the world will consider it legitimate only when convinced that it is being used for the right purpose -- for broadly shared aims -- in accordance with broadly accepted norms."

He said the United States was a model democracy "in which everyone, including the most powerful, is subject to legal restraint."

"Its current moment of world supremacy gives it a priceless opportunity to entrench the same principles at the global level," he continued.

Annan reminded his audience that Truman had once said, "We all have to recognize no matter how great our strength, that we must deny ourselves the license to do always as we please."

He also cited Truman's statement that "the responsibility of great states is to serve and not dominate the peoples of the world," and noted approvingly how Truman had used U.S. power to face down a threat to international order during his administration.

"He believed strongly that henceforth security must be collective and indivisible," Annan said. "That was why, for instance, that he insisted, when faced with aggression by North Korea against the South in 1950, on bringing the issue to the United Nations and placing U.S. troops under the U.N. flag, at the head of a multinational force."

The Bush administration had a subdued reaction to the speech. "We work well with Secretary-General Annan on a number of different issues," said Sean McCormack, the State Department spokesman. "There are some issues on which we disagree. That is to be expected."

Annan paid his final visit to Washington as secretary-general last Tuesday when President Bush gave a dinner in his honor at the White House. One of the guests was John Bolton, the U.S. ambassador who had frequently criticized the secretary-general and who had announced the day before that he was resigning.